Rodent Ulcers in Cats

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Waking up to find that your cat suddenly has a red, angry-looking sore on their lip can certainly seem like a veterinary emergency. If anything, it can't be comfortable for your cat, right? This lip lesion may be something called a rodent ulcer and, while not an immediate emergency, they do require veterinary medical attention.

What are Rodent Ulcers in Cats?

Rodent ulcers, sometimes called indolent ulcers, are severe-looking lesions that arise on your cat's upper lip. They are also one of the three maladies that comprise something called an Eosinophilic Granuloma Complex (EGC). Eosinophilic plaques and eosinophilic granulomas are the other two types of lesions associated with EGC.

Rodent ulcers can vary in size but the edges of the ulcer are well-defined. They are characterized by thickened tissue with raised edges and ulcerated depressions. They can be on one upper lip or both and, despite their alarming appearance, are normally not painful.

The name 'rodent ulcer' comes from an old, incorrect belief that these lesions were caused by the bite of a mouse or rat. Some veterinary professionals have taken to calling them indolent ulcers so as not to contribute to this myth. In fact, in the world of pathology, indolent actually means non-painful and relatively benign.

What Causes Rodent Ulcers in Cats?

While not actually caused by a rodent bite, there are several things that can cause rodent ulcers. These can include bacterial infections, a flea or food allergy, a fungal infection, autoimmune disorders, feline leukemia, or even hypersensitivity to mosquito bites. While there is no breed disposition for rodent ulcers, they tend to appear more often in female cats that are six years old or younger.

How are Rodent Ulcers in Cats Diagnosed?

Since rodent ulcers have a very distinct presentation, diagnosing them is pretty straightforward.

Oftentimes your cat's clinical symptoms and physical exam findings are enough for your vet to pinpoint what's going on. If a more definitive diagnosis is needed or desired, your vet may take cytology samples. These samples may be obtained either with clear tape or something called a fine needle aspirate (FNA).

An FNA entails inserting a needle into the lesion to collect cells and then looking at those cells under the microscope. Although rodent ulcers aren't
normally painful, they are in a location that doesn't lend itself well to needle aspirates. The area around your cat's face may be more sensitive to a needle poke and they may also be uncomfortable with a needle being close by their face.

How are Rodent Ulcers in Cats Treated?

Treatment of your cat's rodent ulcers will depend on what the underlying cause is. Since a hypersensitivity to ectoparasites (that is parasites that live outside the body, such as fleas and mosquitos) is a common cause of them, keeping your cat up to date on their flea and tick medication is a must. This prevention should be given on time and year-round to prevent any lapse in coverage.

Most pet owners know the importance of flea prevention in the summer months, but it may surprise you to know that veterinary offices see an uptick in flea infestation in the fall. This is because, as the outside temperatures drop, the fleas try to hitch a ride indoors where it's warmer.

There are a variety of over-the-counter flea and tick products and not all are the same or necessarily even safe for your cats. Avoid anything with pyrethrin as this is toxic for cats. Also, ensure that you are purchasing a product that is in the proper weight range for your cat. Your vet can recommend which products are worth your money and which to avoid.

The other common cause of rodent ulcers in cats is a food allergy. Just like dogs, cats can be allergic to certain animal proteins. If your cat has rodent ulcers, feeding them commercially available limited ingredient diets or prescription, hydrolyzed diets can help reduce the severity and frequency of ulcers.

If your cat has an active flare-up, your vet may want to start them on a course of antibiotics. They may also start them on a short course of steroids to help with the inflammation. Long term steroid use in cats can be hard on their organs, so your vet will help you find the lowest effective dose.

If other disease processes such as feline leukemia, autoimmune disorders, or fungal infections are contributing to your cat's rodent ulcers your vet will discuss treatment options for those with you as well.

Rodent, or indolent ulcers, while scary in appearance, truly are non-painful and benign. They don't heal on their own, though, so if you suspect your cat has one, speak to your vet about how to treat them and prevent them in the future.